Renewable energy is an option to take very much into account nowadays. Among them, one of the most efficient is wind power, which allows electricity to be obtained from the wind using windmills or wind turbines. Said wind turbines are generally formed of a tower, a gondola, a rotor and some arms; where the wind turbine tower supports the gondola and the rotor. For large wind turbines, the tubular towers can be made of steel, lattice truss or reinforced concrete. Tubular towers tensioned with wind are only used with small wind turbines (battery chargers, etc.).
Different types of towers exist, such as modular towers, as described in European Patent No. ES2272954T3 in the name of Mecal Applied Mechanics B.V., where a modular tower is disclosed consisting of dividing the tower into different annular sections, each annular section being constructed so as to put various modules together with others, stacking the annular constructed sections one on top of the other.
In Spanish Utility Model No. ES1058539U in the name of Inneo21, S.L., a modular tower is also disclosed resulting from the approach to divide the tower into annular sections with each section constructed with various modules put together.
Likewise, in European Patent No. EP1561883B1 in the name of Corus Staal BV, a metallic modular tower is disclosed composed of metallic sections that are substantially quadrangular and placed in a stepped position.
International Publication No. WO 2009/056969 discloses an assembly system of a reinforced concrete tower consisting of assembling an inner metallic structure that has the function of supporting the segments to be fastened to, once raised one by one into position, until the vertical joints are produced.
In said wind turbine towers, sometimes it may be necessary to use damp joints between the elements of prefabricated reinforced concrete, which consist of pouring or injecting mortar or grout into a slot in the sides of the prefabricated elements. Spanish Utility Model No. ES1060629U in the name of Inneo21, S.L., for example, discloses joints of this type.
Generally speaking, reinforced concrete operates better under compression than under traction. As such, it is common to incorporate tensioning cables, which subject the reinforced concrete structure to compression, as it can be possible with a tower structure for wind turbines made of reinforced concrete. Disclosed in the state of the art are cables in the interior of the reinforced concrete modules, as in International patent application WO 86/02689A1, or outside the interior surface of the tower, as in French Patent No. FR508598A. Passing the cables through the interior of the modules is a task which complicates the assembly of the towers, while to pass them over the interior surface of the tower presents the problem of interference of the cables with the many elements that compose a wind turbine tower (e.g., platforms, stairs, lifts, electric equipment and accessories, etc.) and lower effectiveness: with the same tension in the cables a lower moment of compression is achieved, which entails the need to use a greater number of cables.
On the other hand, in patents such as U.S. Pat. No. 5,072,555, tensioning systems are disclosed on the exterior of a tower which are fixed to the ground at a distance from the base of said tower; the cables placed as such modify the dynamic behavior of the structure, modifying the oscillation frequency and limiting its movement.
As disclosed above, dividing a section of truncated conical tower into equal modules, such as reinforced concrete modules, has the disadvantage that the space between the two modules is narrower at the upper part than the part which is supported on the module below; as a result, it is not possible to insert the following module following a totally or partially vertical trajectory. For example, in European Patent No. ES2272954T3, a tower is disclosed which has a cross section which is a polygon or a circle, whose diameter decreases towards the upper part, so that a conical finished shape is achieved or approached. The only way of inserting the new module is by following a trajectory with a horizontal component, which complicates the assembly considerably. In European Patent No. ES2272954T3, reference is made to the disadvantages associated with the manufacture of a conical tower, overcome with the implementation of the object of this invention.
Similar disadvantages are found with a tower with stepped modules where the tower has a circular cross section, with one or more rings of the tower being stepped so that the exterior diameter and/or the thickness of the wall of an upper ring is less than the respective lower ring, making the vertical assembly of the following module impossible.